In the manufacture of an electronic device, etching is performed to remove a certain region of a processing target object selectively. For example, a first region made of silicon oxide is selectively etched with respect to a second region which is formed of silicon nitride. A method of etching the first region selectively with respect to the second region is described in Patent Document 1.
On the processing target object to which the method described in Patent Document 1 is applied, the second region is extended on an underlying region to provide a recess. The second region has a bottom region. The bottom region is extended at a bottom of the recess. The first region is configured to cover the second region. In the method disclosed in Patent Document 1, plasma of a processing gas containing fluorocarbon is generated, and a deposit containing the fluorocarbon is formed on the processing target object. Then, plasma of a rare gas is generated, and ions of rare gas atoms are supplied to the processing target object. The deposit protects the second region. Meanwhile, the fluorocarbon in the deposit etches the first region if the ions of the rare gas atoms are supplied to the processing target object.
Patent Document 1: Japanese Patent Laid-open publication No. 2016-136606